( 504 ) 



only one or two, in the latter case the second being placed at the apex of the 

 elytra. The missing comb or combs are represented by a row of bristles. 



The first segment of the antenna of the Old- World Poli/cteniclae has a smaller 

 number of thick stumpy spines in the immatnre specimens wo have examined than 

 in any of onr adults, or has only bristles (PI. XII. fig. :!). The only young American 

 e.xample we have before us, however, has a comb of sjiines on the first antennal 

 segment which is not present in adults of tlie same genus, the individual as a 

 compensation lacking the gular comb. It is interesting to note that the gular 

 comb, though i)resent in our immatnre individuals from Asia and Africa, in these 

 examples does nut extend so far backwards at the sides of the head as in the most 

 nearly allied adults. 



These are general statements in which no cognisance is taken of the question 

 whether any of the young specimens belong to any of the species represented 

 by our adult individuals, or whether they are immature forms of which the 

 adults are not yet known. As we have to assign a place in classification to each 

 individual before us, i.e. as we have to decide whether an immature specimen 

 belougs to one of the adults or to a separate species, we must ask what guide we 

 have in arriving at a decision. From the above statements so much is certain, that 

 an immature individual which is similar to an adnlt one, but exhibits some such 

 deficiencies as are mentioned above, must not be considered a distinct species on 

 account of these deficiencies alone. Therefore, if adult and immature specimens 

 which are obtained from the same host and in the same locality differ only in that 

 way, one can be tolerably sure that they belong to one and the same species. As 

 an instance we refer to the two forms represented by figs. 1 and 3 on PI. XII. Both 

 specimens were found in the British Museum in a jar with bats from China, and 

 one is adult (a ?) and the otlier immatnre. The original s])ecimeus of /'o/,yc^'«('.y 

 molossas which tiiglioli collected on a bat at Amoy are tin's same sjiecies, and 

 curiously enough one also is immature and the other (but this time a S) adult. 

 Here, we think, there can be no doubt that the differences between the two 

 sjiecimens are only due to the difference in the degree of maturity. 



As in most cases the newly formed epidermis, with its hairs and spines, can 

 be seen within the old skin of the immatnre examples, one must expect to meet 

 with individuals in which the old skin has the characters of the pupal stage and 

 the new skin those of the imago. If we are right in considering figs. 1 and 3 as 

 depicting difterent stages in the metamorphosis of one species, individuals must 

 occur which have no combs on the upper surface, like fig. 3, while beneath the skin 

 the newly forming combs of fig. 1 are visible. Now it is a curious fact that 

 in Westwood's figure of a non-adult specimen, and in those of onr immature 

 individuals where the bristles and spines of the new skin are at all distinguishable, 

 the newly forming skin does not exhibit any obvious differences from the (dd one. 

 We can only explain this fact by assuming that the young Polyctenid is born with 

 a certain skin armature which does not essentially change at the larval moults, 

 the chief larval characteristics being j)reserved until llie later moult. However, 

 the stage in the life-history of the mdividual which is missing in the collection 

 of the British Museum was discovered two years ago by Dr. ISpeiser, who received 

 for description a specimen from the Indian Museum, which proved to be a nymph 

 before the final moult. This si)ecimen is described as having dorsally only one 

 comb, which is placed at the hind edge of the head. But under the skin 

 ])r. Speiser found the newly forming imago with a distinct comb on the pronotum 



